This invention relates to dispersions of tetrafluoroethylene/hexafluoropropylene (TFE/HFP) copolymers. It is more particularly directed to stable, substantially anhydrous dispersions of TFE/HFP copolymers in organic liquids, to blends of these dispersions with other film-forming materials, and to articles coated with films of these dispersions.
Aqueous dispersions of TFE/HFP copolymers have been known for some time and have been extensively used to coat and impregnate articles with these polymers. These aqueous dispersions, however, have a tendency to coagulate irreversibly when subjected to excessive heat, freezing, mechanical agitation, or on the addition of electrolytes or water soluble solvents. They are also difficult to bond firmly to metal substrates without expensive and bothersome pretreatments.
In an attempt to prepare compositions without these shortcomings, dispersions of these copolymers have been prepared in organic liquids. These dispersions, however, have been unsatisfactory because they coagulate undesirably and settle quickly. This makes them unsuitable for commercial use.
The dispersions of this invention have none of these shortcomings. They are remarkably stable to coagulation, resist settling, and moreover, permit firm bonding of coatings to metal substrates without the pretreatment required when aqueous dispersions are used.